The most common way to connect a flat flexible cable (FFC) to circuit pads on a printed circuit board is via connectors soldered to the board. These connectors are usually mounted on the circuit board at a distance away from the edges of the board, such that the contact legs of the connectors can extend through openings provided in the board, thereby allowing wave soldering to occur. It is not unusual to have ten to twelve connectors soldered to various locations on the board.
In order to reduce the size of the printed circuit board, there is now a trend to remove these connectors from the top and bottom surfaces of the circuit board, and at the same time eliminate the soldering operations associated with them. Such a solution requires that the circuit paths be extended so that the circuit pads which are be electrically connected to the connector are position proximate the edges of the circuit board. Utilizing the edge of the board for the interconnection allows the electrical connector to be electrically connected to the circuit board without the need for solder. The use of the edge of the board also allows the top and bottom surfaces to accommodate other valuable pieces of circuitry.
A significant problem with edge connectors which are utilized to terminate high density FFC relates to the fact that it is extremely difficult to terminate the FFC without damaging the individual conductors of the cable. Various attempts have been made to pierce through the very fragile conductors and stake or fold the piercing legs subsequent to penetration. Understandably such terminations are very unreliable.
Another consideration with edge connectors is the lateral position of the connectors must be accurately controlled in order for the contacts of the connector to make proper electrical contact with the circuit pads of the printed circuit board. Attempts to position the connector by milling slots about the board edges have proven to be expensive and impractical.
An associated problem with edge connectors relates to the problem of locking the connectors to the board. It has proven difficult to lock the connector to the board in such a manner as to insure that an electrical connection will be provided over time.